The present invention pertains to a dispensing appliance for at least two components, comprising a pump assembly with a housing containing a metering cylinder for each component, each metering cylinder having an inlet and an outlet and a displacement plunger, each of the inlets being connected to a container which holds one of the components and the outlets of the pumps ending in a common outlet, the pump assembly being held in a frame comprising frame plates on the dispensing side and on the drive side thereof, the plates being detachably connected to each other by means of tie rods, in particular to a compact hand-held appliance.
Such an appliance is known from European Patent Application No. 607,102, disclosing rather schematically the principles of an appliance with a frame and housing which can be easily dismantled and reassembled. This is also the case for the path of the outlets of the cylinders into the common outlet nozzle, which is relatively long and contains therefore a relatively high volume of liquid which can cause air bubble entrapment. There is no defined sealing between the metering cylinder front face and the double outlet and therefore pressure can build up between their respective plane surfaces resulting in an axial force compressing the internal parts including seals contained in the pump housing.
In the above mentioned appliance for two components, the pairs of metering cylinder/displacement plunger combinations for achieving different ratio do not provide uniform metering pressures for the different ratios.
Furthermore, within the pump housing, the internal assembly of rear spacers, rear displacement plunger seals, inlet spacers, metering seals and metering cylinders may be axially compressed without limitation by the tie rods, resulting in uncontrollable friction between metering seals and displacement plungers thus reducing available pump pressure and allowing a variation in seal efficiency and potential damage to those seals.
PCT/GB92/00813 discloses an appliance, referring however primarily to the storage container, while U.S. Pat. No. 4,690 306 discloses a method and device for storing, mixing and dispensing of at least two fluid substances, wherein the device is assembled in a sort of frame with relatively complicated pieces, and the containers are disposable.
As with most developing technological products, there comes a time for standardization of requirements and specifications such that the production of high cost "one off" equipment can, in the main, be replaced by mass produced and relatively low cost units. The field of high performance multi component reactive chemical systems such as epoxies and polyurethanes is no exception with the use of pumping, metering, mixing and dispensing machines. Such machines tend to be relatively expensive and technically complicated whereas the ideal is to reduce the complexity and cost of a multi component system to that of a single component system. The need, therefore, is for machines to be standardized around a basic operating specification, which makes them simple to use, compact, lightweight as hand held portable devices for use with relatively low volume exchangeable chemical component packages for low volume dispensing applications, yet are easily convertible to bench or robot mounting with direct feed of the chemical components from larger containers for higher volume dispensing applications. Also there is the need to provide for interchangeable parts to cover the many different relative mixing ratios of the chemical components and for a quick disassembly of all parts for ease of servicing.
Finally, a high degree of performance and reliability is required while providing both accurate relative metering ratios and the necessary accuracy of the simultaneous start of flow of both metered chemical component streams through a static mixer at the time of dispensing commencement. The latter being preferably achieved by the ratio metering taking place immediately before the mixer and therefore close to the point of dispensing of the mixed chemical components, thus avoiding undue compression of non hydraulic chemicals and resultant inaccuracy of metering due to conventional long conduits between the metering pumps and the point of dispensing.